Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$10.61	3.759%	$11.0088	$11.01	$11.00	$11.00
Purchase #2	$20.93	5.649%	$22.1123	$22.11	$22.10	$22.10
Purchase #3	$102.89	11.770%	$115.0002	$115.00	$115.00	$115.00
Purchase #4	$246.72	11.584%	$275.3	$275.30	$275.30	$275.30
Purchase #5	$131.60	4.316%	$137.2799	$137.28	$137.30	$137.30
Purchase #6	$188.44	6.322%	$200.3532	$200.35	$200.35	$200.40
Purchase #7	$94.42	11.630%	$105.401	$105.40	$105.40	$105.40
7 purchase totals =	$795.61		$866.4554	$866.45	$866.45	$866.50